Hydraulic apparatus



Jan. 9, 1968 Filed June J. c. E. FLINT ETAL HYDRAULIC APPARATUS 5 Sheets-Sheet 1 Iuvau-roz (fa/m c E. F/ m 324, w. EuQweff M m C'KMM A-r-rcrapav Jan. 9, 1968 J. c. E. FLINT ETAL. 3,

HYDRAULI G APPARATUS Filed June 7, 1965 5 Sheets-Sheet 2 Iuv tau-r012 By John c5. F744- 7041. Lu Elferell 04,240.62 m, MTW

1968 J. c. E. FLINT ETAL 3,362,342

HYDRAULI C APPARATUS Filed June 7, 1965 5 Sheets$heet 3 IIuvEw-roE Y J01 C.. 7 4 E a 5 Awmeuav United States Patent Filed June 7, 1965, Ser. No. 461,650 Claims priority, application Great Britain, June 12, 1964, 24,404/64 7 Claims. (Cl. 103-162) This invention relates to hydraulic apparatus and more particularly to hydraulic pumps or motors of the rotatable cylinder barrel, reciprocable piston, kind, in which delivery in the case of a pump, or admission in the case of a motor, is varied by adjustment of an angularly-displaceable valve member co-operable with the rotatable barrel and including high pressure and low pressure ports, themselves having bridge portions formed between them, which adjustment changes the relationship between the positioning of the ports and the stroke posltioning of the pistons within their cylinders in the barrel. A pump or motor of this kind is hereinafter referred to as a pump or motor of the kind described.

According to this invention a pump or motor of the kind described and which has an odd number of pistons and cylinders, includes a liquid reservoir which is in permanent communication with openings, at least one such opening being formed in each bridge portion in the valve member, cylinder ports, provided in the cylinder barrel adjacent the valve member, which ports are co-opera'ble with the high pressure and low pressure ports, and are each of such arcuate length in the circumferentlal sense as to be capable, when passing in registry with each opening, of momentarily providing overlapping communication between that opening and either its adacent high pressure or its adjacent low pressure port without forming a leakage path between the high pressure and the low pressure ports.

The liquid reservoir may be housed within a part of the casing of the pump or motor, or may instead be housed within the valve member itself.

The valve member may include a single high pressure port and a single low pressure port, two bridge portions being formed between these ports.

It is intended that the liquid reservoir has a desired amount of fluid pressure energy storage capacity, the compressibility of the liquid giving rise to a resilient factor. Alternatively, the reservoir may be itself made of an elastic material to afford an additional resilient factor. Again, the reservoir may be provided with a flexible wall backed by spring means to afford the additional resilient factor.

Where the pump or motor is of the axial-piston, fixed swash-plate type, the valve member is in the form of a valve plate co-operable with the cylinder barrel and angularly displaceable about the rotational axis of the barrel.

Where the reservoir is provided in a part of the casing of the pump or motor other than the valve member, it may be housed within the head member of the pump or motor, the two openings in the bridge portions between the high pressure and low pressure ports being in communication with the reservoir through a rotary bearing.

During operation of the pump or motor excess pressure build-up within each cylinder as it passes in registry with one or other of the bridge portions is at least substantially obviated because this build-up is absorbed 3,362,342. Patented Jan. 9, 1968 by the reservoir, while cavitational effects in the cylinder otherwise occurring as the cylinder passes in registry with one or other of the bridge portions, are at least substantially obviated because the built-up pressure absorbed by the reservoir is available to pass into that cylinder where cavitational conditions are tending to be set up.

The relationship between the angularly displaceable valve member, the odd number of cylinder ports in the rotatable cylinder barrel, and the openings in the bridge portions, may be such that the reservoir receives liquid from those pistons advancing in their cylinders as their cylinder ports pass across the opening in one bridge portion; and the reservoir also discharges liquid into those cylinders whose pistons are receding in their cylinders as their cylinder ports pass across the opening in the other bridge portion.

Such transfer of liquid is out-of-phase so that the res ervoir must have accumulation capacity, high pressure liquid being momentarily stored in the reservoir for discharge at appropriate instants into the cylinders where the pistons are receding in order to avoid cavitation.

One embodiment of the invention will now be particularly described with reference to the accompanying drawings, of which:

FIGURE 1 is a cross-sectional side elevation of a swash-plate type pump in accordance with the invention, and,

FIGURES 2, 3, 4 and 5 are diagrammatic representations of the valve plate of the pump shown in FIG- URE 1, these drawings showing in sequence the timed relationship between ports in the valve plate of the pump and ports in the rotatable cylinder barrel of the pump.

Referring to FIGURE 1 of the drawings, a swashplate type pump comprises a casing 11 housing a rotatable cylinder barrel 12 arranged to be driven by a shaft 13. The rotatable cylinder barrel 12 has nine ax ially-directed cylinders 14, each containing a piston 15, all of which by virtue of a fixed swash-plate 16 reciprocate in their cylinders upon rotation of the cylinder barrel. A slipper 17 is provided for each piston, being universally jointed at 18 and being in sliding engagement with the face 19 of the swash-plate 16.

Each piston 15 is provided with a spring 20 and the end portions of the cylinders 114 remote from the swashplate are each provided with a cylinder port 21, all of these cylinder ports being co-operable with high pressure and low pressure ports (not shown) formed in a valve member in the form of a circular valve plate 22.

The valve plate 22 is angularly-displaceable about the axis 23 of rotation of the pump, and around its periphery is provided with gear teeth 24 which are engaged by a pinion (not shown), rotation of which affords the angular displacement of the valve plate.

A head member 25 forms a closure member for the casing 11 and carries a plain journal bearing 26 which supports the shaft 13 and the valve plate 22.

Pump inlet and outlet ports (not shown in FIGURE 1) are provided in the head member 25 in registry with the main low pressure and high pressure ports in the valve plate 22. I

Secured to the head member 25 and circumferentially surrounding the valve plate with suitable operating clearance is a ring member 27. Fitted to this ring member in a manner so as to be co-operable with that face of the valve plate remote from the head member is a reaction member 28.

The valve plate 22 is thus by this construction interposed between the head member 25 and both the rotatable cylinder barrel 12 and the reaction member 28, sufiicient Working clearance being provided for the valve plate to be angularly displaceable throughout a range of adjustment approaching 90 degrees. The high pressure and low pressure ports in the valve plate are of kidney shape, two bridge portions 29 and 30 being formed in the valve plate between them. Openings 31 and 32 are respectively provided in these bridge portions 29 and 30, these openings being co-operable with the cylinder ports 21.

The valve plate 22 is arranged to be maintained in substantial hydrostatic balance.

The openings 31 and 32 in the bridge portions 29 and 30 are both in communication, respectively, through radial ports 33 and 34 in the valve plate, with an annulus 35 formed in the bearing 26. Sealing rings 36 and 37 are provided on either side of this annulus. At a position axially displaced from the annulus 35, the bearing is provided with a further annulus 38 which is, in registry with a port 39 formed in the head member 25. This annulus 38 also has sealing rings 40 and 41 provided on either side of it. A passageway 42 connects the annulus 35 with the annulus 38.

The port 39 opens into a liquid reservoir 43 formed in the head member, this reservoir having a closure plug 44 screw-threadedly fitting into it.

Thus the arrangement of annuli 35 and 38, and the passageway 42 form a rotary hearing which places the openings 31 and 32 in the bridge portions permanently in communication with the liquid reservoir 43.

The basic operation of the pump is such that upon rotation of the shaft 13, together with the cylinder barrel 12, reciprocation of the nine pistons in their cylinders 14 occurs, hydraulic liquid being drawn in through the inlet port in the head member 25 and being discharged under high pressure from the pump through the outlet port (not shown) in the head member. The volume of liquid delivered from the pump depends upon the angular setting of the valve plate 22, this being movable through the range approaching 90 degrees from a position appropriate to low delivery to a position appropriate to full delivery. In this way there is provided means for varying the relationship between the positioning of the porting of the valve plate and the stroke positioning of the pistons within their cylinders. Since there is a definite positional relationship, due to the fixed swash-plate, between each of the pistons and cylinders of the rotatable cylinder barrel, then upon angular displacement of the valve plate there must be a change in the delivery of the volume from the aggregate of the cylinders, because a change in the phasing between the high pressure and low pressure kidney ports and the stroking pistons is elfected.

With the valve plate 22 in the full delivery position, the high pressure kidney port is connected only to pistons delivering liquid. As the valve plate is rotated towards its low flow condition, a progressively fewer number of pistons connected to the high pressure kidney port are delivering, while a progressively larger number are receiving liquid. Thus there is an interchange of liquid Within each kidney port between pistons advancing and pistons receding. At all positions of the valve plate, except that corresponding to zero delivery, the quantity displaced by the advancing pistons is greater than that required by receding pistons, the balance appearing as delivery at the pump outlet. Hence, delivery of the pump is varied without varying the length of the stroke of the pistons.

Although the high pressure and low pressure kidney ports are not shown in FIGURE 1, they are shown in FIGURES 2, 3, 4 and 5.

Referring now to FIGURES 2, 3, 4 and 5, the reservoir 43 in each of these drawings is shown diagrammatically, the radial ports 33 and 34 also being shown diagrammatically and as connecting from their associated openings 31 and 32 directly with the reservoir.

The high pressure kidney port in the valve plate 22 is shown at 45, while the low pressure kidney port in the valve plate 22 is shown at 46, the bridge portions 29 and 30 indicated in FIGURE 1 being formed between these kidney ports and respectively incorporating the openings 31 and 32.

The nine cylinder ports 21 formed in the rotatable cylinder barrel 12 are also shown in FIGURES 2, 3, 4 and 5, but in each of these figures the rotational position of the cylinder barrel has changed in the direction of the arrow 47 so that the ports 21 have a different positional relationship with respect to the kidney ports 45 and 46 and the openings 31 and 32 in each of these drawings.

Referring firstly to FIGURE 2, and assuming that the valve plate 22 is held in the position shown appropriate to a certain delivery condition of the pump so that the kidney ports 45 and 46 are in a fixed position, the rotatable cylinder barrel 12 is in a rotational position such that the cylinder port A slightly overlaps the high pressure kidney port 45 and also overlaps the opening 31 in the bridge portion 29. It will be seen that the arcuate length of each cylinder port 21 is slightly greater than the distance between the extremity of a kidney port and the adjacent edge of the respective opening 31 or 32.

By virtue of the fact that there is an odd number of cylinders in the pump, the cylinder port B which is almost opposite to the cylinder port A can be seen in FIGURE 2 in registry with only the opening 32.

Thus, in the condition shown in FIGURE 2, the cylinder port A is in communication with the reservoir 43 and also in communication with the high pressure kidney port 45, while the cylinder port B is in communication with only the reservoir. Thus, since the piston associated with the cylinder port A is receding in its cylinder, that is, moving in a direction away from the cylinder port, but for the provision of the opening 31 cavitation in that cylinder would occur, This opening, however, permits liquid momentarily stored under pressure in the reservoir (this by virtue of the compressibility of the liquid), to pass into that cylinder together with a small quantity of high pressure liquid derived from the high pressure kidney port 45. On the other side of the valve plate, the piston in the cylinder associated with cylinder port 'B is advancing towards the valve plate and but for the provision of the opening 32 and its connection with the reservoir, an undesirably high pressure peak would occur as this port is passing the bridge 30. However, the reservoir 43 absorbs such a high pressure peak and depending upon the capacity of the reservoir, a certain proportion of the pressure energy as mentioned above (by virtue of the compressibility of the liquid), is stored, the remainder being conducted directly into the cylinder associated with the cylinder port A.

Referring now to FIGURE 3 which shows the position of the cylinder ports 21 when the rotatable cylinder barrel 12 has moved slightly further in its rotation, the cylinder port A is no longer in communication with the high pressure kidney port 45 but presents a larger efiective area to the opening 31 to enable a larger flow to occur from the reservoir 43 in the cavitation-avoiding function. At the same time, the cylinder port B has moved to a position in which the area it presents to the opening 32 has reduced somewhat so that the flow of high pressure liquid into the reservoir 43 is reduced.

With reference to FIGURE 4, the cylinder port A has moved still further in its rotation so that a maximum area is presented to the opening 31. Thus the cylinder associated With the cylinder port A is receiving a maximum flow of liquid in the cavitation-avoiding function. At the same time the cylinder port B is now presenting a very much smaller area to the opening 32 and is also cracking open communication with the high pressure kidney port 45. Under these conditions the charging of the reservoir 43 from the cylinder port B is greatly reduced and in the 5. cavitation-avoiding function of the reservoir the momentarily-stored pressure energy is now being utilised.

Referring now to FIGURE 5, the cylinder port A is now in a position such that the opening 31 is positioned mid-way along the length of the port A, while the cylinder port B is no longer in communication with the opening 32 but is in full communication with the high pres sure kidney port 45. The opening 32 is thus closed by the bridge portion 30 so that no pressure charging of the reservoir is occurring. However, the cavitation-avoiding function is continuing utilising the stored pressure energy within the reservoir 43.

Although not shown in the drawings, further rotational movement of the cylinder barrel results in movement of the cylinder port A so that closure thereof with respect to the reservoir occurs, but this port opens to the low pressure kidney port 46. A little further in the sequence the cylinder port C (shown in FIGURE places the reservoir in communication with the low pressure port momentarily. However, as this cylinder port C moves towards the high pressure port 45 across the opening 32, pressure build-up again occurs by virtue of the advancing piston in the cylinder associated with the port C.

As the port A is opening to the low pressure kidney port 46, the port D (see also FIGURE 5) takes up a p0sition similar to that for port A in FIGURE 2 and the arrangement again functions as above described.

Thus, in operation of the reservoir three types of connections are afforded. These are (i) cylinder port to kidney port (designated K), (ii) cylinder port to reservoir (designated R), and (iii) cylinder port to both kidney port and reservoir, designated KR (or RK).

Using these designations, the following table sets out the operating sequence, the side of the arrangement including cylinder port A, with respect to the side of the arrangement including the cylinder port B:

Side including Port A Side including Port B Figure No.

K (High Pressure) Thus, in general the reservoir 43 receives liquid from the port B advancing over the bridge portion 30 and discharges liquid into the port A whose piston is receding. Such functioning is out of phase so that it is necessary for the reservoir to have accumulation capacity.

The maximum capacity required of the reservoir is determined by the liquid flow from a cylinder delivering into the bridge opening at zero pump delivery and at the time when the opposite bridge opening is disconnected from a cylinder. Similar requirements occur when the piston is sucking at maximum velocity from the bridge opening instead of delivering (see FIGURE 5).

When both bridge openings are connected to cylinders in which one piston is advancing and one is receding, less reservoir capacity is required but since the pistons are moving in and out at different speeds some capacity is necessary.

Where one cylinder port connects one bridge opening to a kidney port and the other cylinder port connects only to the bridge opening, the difference between the two pis- 70 ton instantaneous flows will be made up or delivered almost entirely by the kidney port, the part played by the reservoir being only relative small.

Although in the above-described embodiment the reservoir 43 is incorporated in the head member of the pump,

6 in an alternative embodiment of the invention, the reservoir is incorporated in the angularly displaceable valve member itself.

Again, although in the above described embodiment the reservoir is simply a cavity formed in the casing, absorption of energy there being afforded by the compressibility of the liquid, in an alternative embodiment of the invention, the reservoir is defined by a container made from resilient material of Such nature that pressure energy is also absorbed in the material itself.

In yet a further alternative embodiment of the invention, the reservoir is formed by a cavity in the casing, but having a wall thereof resiliently mounted, for example, backed by a resilient ring, to afford pressure energy storage therein as well as in the liquid itself.

Although in the above embodiment described with reference to the drawings the invention is applied to a hydraulic pump, in other embodiments the invention is with advantage applied to hydraulic motors, or, again, to transmission apparatus combining both hydraulic pumps and motors.

Also, the invention is in no way limited to pumps or motors of the axial-piston type, as in other embodiments it is with advantage applied to pumps or motors of the radial-piston type.

By the invention, it is ensured that no leakage path is formed from the high pressure port to the low pressure port in the valve member.

What we claim is:

1. In a fluid energy translating device of the type comprising a casing with a pump or motor mechanism therein including a rotary cylinder barrel having a plurality of cylinders with pistons slidable therein operatively associated with camming means for reciprocating the pistons, each cylinder having a port opening to a valve face of the cylinder barrel, the improvement comprising a liquid reservoir formed within a part of said casing, and a valve member having a valve face in fluid sealing engagement with the valve face of the cylinder barrel, and high pressure and low pressure ports therein which are in operative communication with the cylinder ports, and spaced apart from one another to form bridge surfaces therebetween which are disposed opposite the rotary path of but closed to the cylinder ports, there being a pair of passages in the valve member which terminate at openings in the bridge surfaces, and continuously interconnect the openings with the reservoir, so that there is a continual flow of liquid through the reservoir from one opening to the other as the cylinder barrel is rotated, the reservoir being closed to atmosphere and the cylinders being odd in number so that the liquid is pressurized by pistons on the power stroke as the cylinder ports thereof pass the aforesaid one opening, and the two openings in the bridge surfaces being interconnected with the reservoir through a ported rotary bearing formed in a plain journal bearing which is carried in said casing part and supports for rotation one end portion of a shaft upon which the rotary cylinder barrel is secured, said rotary bearing comprising two connected annuli formed in the journal bearing, the first annulus being in alignment with passageways in the valve member which communicate with said openings, and the second annulus being in alignment with a port in the casing part, which latter port is in communication with said liquid reservoir.

2. The device claimed in claim 1, wherein the face of the valve member has a single high pressure port and a single low pressure port therein, two bridge surfaces being formed between these ports.

3. The device claimed in claim 1, wherein a port-ion of the journal bearing forms carrier means upon which the valve member is supported for angular displacement.

4. A fluid energy translating device according to claim 1 wherein the valve member is rotatably mounted to vary the displacement of the pump or motor mechanism.

5. A fluid energy translating device according to claim 7 4 wherein each of the cylinder ports has an arcuate opening in the direction of rotation of the cylinder barrel, adapted to overlap simultaneously with either of the bridge surface openings and the adjacent high pressure or low pressure port in the valve member.

6. The device claimed in claim 4, wherein the range of angular displacement of said valve member between low flow and high flow conditions is substantially 90 degrees.

7. The device claimed in claim 4, wherein the valve member is provided with gear teeth with which a pinion is in mesh, rotation of the pinion aflording angular displacement of the valve member.

References Cited UNITED STATES PATENTS 10 DONLEY J. STOCKING, Primary Examiner.

ROBERT M. WALKER, Examiner.

W. L. FREEH, Assistant Examiner. 

1. IN A FLUID ENERGY TRANSLATING DEVICE OF THE TYPE COMPRISING A CASING WITH A PUMP OR MOTOR MECHANISM THEREIN INCLUDING A ROTARY CYLINDER BARREL HAVING A PLURALITY OF CYLINDERS WITH PISTONS SLIDABLE THEREIN OPERATIVELY ASSOCIATED WITH CAMMING MEANS FOR RECIPROCATING THE PISTONS, EACH CYLINDER HAVING A PORT OPENING TO A VALVE FACE OF THE CYLINDER BARREL, THE IMPROVEMENT COMPRISING A LIQUID RESERVOIR FORMED WITHIN A PART OF SAID CASING, AND A VALVE MEMBER HAVING A VALVE FACE IN FLUID SEALING ENGAGEMENT WITH THE VALVE FACE OF THE CYLINDER BARREL, AND HIGH PRESSURE AND LOW PRESSURE PORTS THEREIN WHICH ARE IN OPERATIVE COMMUNICATION WITH THE CYLINDER PORTS, AND SPACED APART FROM ONE ANTOHER TO FORM BRIDGE SURFACES THEREBETWEEN WHICH ARE DISPOSED OPPOSITE THE ROTARY PATH OF BUT CLOSED TO THE CYLINDER PORTS, THERE BEING A PAIR OF PASSAGES IN THE VALVE MEMBER WHICH TERMINATE AT OPENINGS IN THE BRIDGE SURFACES, AND CONTINUOUSLY INTERCONNECT THE OPENINGS WITH THE RESERVOIR, SO THAT THERE IS A CONTINUAL FLOW OF LIQUID THROUGH THE RESERVOIR FROM ONE OPENING TO THE OTHER AS THE CYLINDER BARREL IS ROTATED, THE RESERVOIR BEING CLOSED TO ATMOSPHERE AND THE CYLINDERS BEING ODD IN NUMBER SO THAT THE LIQUID IS PRESSURIZED BY PISTONS ON THE POWER STROKE AS THE CYLINDER PORTS THEREOF PASS THE AFORESAID ONE OPENING, AND THE TWO OPENINGS IN THE BRIDGE SURFACES BEING INTERCONNECTED WITH THE RESERVOIR THROUGH A PORTED ROTARY BEARING FORMED IN A PLAIN JOURNAL BEARING WHICH IS CARRIED IN SAID CASING PART AND SUPPORTS FOR ROTATION ONE END PORTION OF A SHAFT UPON WHICH THE ROTARY CYLINDER BARREL IS SECURED, SAID ROTARY BEARING COMPRISING TWO CONNECTED ANNULI FORMED IN THE JOURNAL BEARING, THE FIRST ANNULUS BEING IN ALIGNMENT WITH PASSAGEWAYS IN THE VALVE MEMBER WHICH COMMUNICATE WITH SAID OPENINGS, AND THE SECOND ANNULUS BEING IN ALIGNMENT WITH A PORTPORT IN THE CASING PART, WHICH LATTER PORT IS IN COMMUNICATION WITH SAID LIQUID RESERVOIR. 